The present invention concerns a filter material for cleaning air and gases, a filter for cleaning air and gases, as well as the use of the filter material in cigarette filters and dedusting and gas cleaning devices.
Filter materials for cleaning air and gases, for short referred to as gas filters, are used in order to remove undesirable suspended particles such as pathogenic germs, pollen, dust or foreign gases from the air or the gas. Important fields of use are dust-emitting industries such as the paper industry and cement industry, use in ventilation devices in order to keep away pollutants from living and working spaces, in vacuum cleaning devices in order to filter the exiting air.
A further field of application is the use as filters in tobacco products, e.g., in cigarettes. The cigarette filter is designed to reduce the proportion of health-hazardous substances such as condensate and gases in the smoke of the cigarette. Moreover, by means of the filter the smoke is becoming somewhat milder so that some smokers remove or shorten it for a more intensive taste. In a classic filter cigarette the filter is enveloped by a cork-colored mouth piece in order to prevent that the brown discoloration of the filter becomes visible. Most industrially manufactured cigarettes are provided with a filter; smokers who make their own cigarettes can buy them in a tobacco shop.
The basic material for producing prior art cigarette filters is cellulose acetate. Cellulose acetate is existing in the form of threads that have a diameter between 30 and 50 μm. They are combined/bundled to an endless band and are spot-wise glued with triacetine. Such a cigarette filter can retain particles up to a diameter of less than 0.2 μm.
The cellulose acetate that is employed in cigarette filters is obtained by chemical modification of cellulose. It is an inexpensive material that also is easy to process. By the chemical modification of the cellulose to cellulose acetate, the fibers are no longer usable as a food basis for microorganisms, i.e., it is resistant with regard to mold, fungi or bacteria attack, but at the same time is also difficult to decompose biologically. The chemical resistance is a disadvantage in connection with cigarette filters because they will decompose or degrade only slowly. Cigarette stubs that are disposed of, i.e., thrown away, in nature remain unchanged for a long period of time and are visible as litter.
European patent EP 1 032 283 discloses a filter cigarette with a biologically decomposable filter. The filter contained in this filter cigarette contains an uncrimped cellulose nonwoven, produced by the “airlaid” process, with normal retention performance and a filter ventilation zone that extends in circumferential direction. This cigarette is supposed to deliver the acetate-typical taste impression and also the acetate-typical visual appearance. In order to obtain these goals, the cigarette must have a specific configuration as disclosed in EP 1 032 283.
Filter materials are however not only important with regard to tobacco products. In industry and in the household there is always the need for new and inexpensive filter materials with which undesirable suspended particles such as pathogenic germs, pollen, dust or gases are to be removed from the exhaust air or, as in case of ventilation devices of living and business spaces, in order to keep pollutants from entering these spaces.
The invention has therefore the object to provide a filter material that combines the advantages of a good filter action with the advantage of being biologically decomposable.